The invention concerns a planetary gear drive.
Such planetary gear drives, wherein the planet carrier forms the output drive, and in common with an output side output shaft is borne by an axially set, inclined bearing pair, are adaptable for the transmission of high forces and torque moments. The drives are employed in combination with a bolt-on electric motor or, among other applications, may be integrated into automatizing technology, wherein, on the output shaft, for example, a toothed pinion or a belt pulley for toothed belts is placed. With the bearing support of the output shaft and of the planet carrier by means of an axially placed, inclined pair of bearings and by means of a corresponding preloading between the bearings, a very high structural strength and precision of the bearing system can be achieved.
In the case of the bearing support by an inclined bearing pair, a difference is defined between a so-called X-arrangement, and a so-called O arrangement of the two sets of installed bearings. In the case of the X-arrangement, pressure lines, which run through the rotating body and intersect at the axis of rotation, represent pressure cones, the apexes of which point to one another. In the case of the O-arrangement, the apexes of the pressure cones formed by the two bearings of the bearing pair point away from each other.
The X-arrangement generally offers the best solution for a simple mounting, a low outlay for construction and a minimum of supervision of design work. The reason for this is that both bearings of the inclined bearing pairs can be so mounted, with their respective inner and outer rings, such that axial contact surfaces on the components, which serve as abutments for the bearing inclines, later in operation can also pick up axial operational loadings. Hence, as a rule, no further axial securement parts for the inner and outer rings of the bearings need be provided or installed. In any case, where the X-arrangement is concerned, the bearing distance for effective bearing kinematics, as well as the separating distance of the apexes of the pressure cones, is shorter than the axial distance of the two bearings. Fundamentally, however, the greatest possible bearing distance for effective bearing kinematics is desirable, in order to achieve a high degree of loading resistance and structural strength, as well as to assure precise running of the output shaft. A drive, in which the planet carrier, which may be of one piece with the output drive shaft, is supported by a bearing pair in the X-arrangement. This, however, is not included in the non-published DE 199 56 789 A1. Because of the above discussed characteristics of the X-arrangement, with this drive, the two installed bearings are placed on both sides of the planetary gear plane, i.e., located on both sides of the planetary gear set, whereby a generally short, axial installation length of the drive is made possible.
Converse to the X-arrangement, the O-arrangement offers a bearing distance for effective bearing kinematics which is greater than is the constructed axial distance of the two bearings. The advantage therein is, that increased loading capacity and structural strength, along with a precise run of the output shaft can be attained. To install the bearings on each side of the planetary gear plane in the O-arrangement, presents, however, serious problems. Since in this case, the pressure on the inclined bearings in the directional sense of an angular movement always lies contrary to the axial directive sense of a later operational loading on the bearing there must also be clearance-free axial securement components necessary for the inner and outer bearing rings, which are difficult to install and increase the demand of the space requirements of the drive. An exact adjustment of the bearing clearance, that is, the bearing preloading at the time of the mounting, is very complex and rife with problems.
EP 0 687 836 shows a planetary drive, wherein the output shaft is supported on a bearing pair in the O-arrangement manner. In the case of this drive, both bearings of the bearing pair are next to one another, and axially disposed on the output side of the actual planetary gear. The inner rings of the two bearings are seated proximal to one another on a section of the output shaft and are loaded by a threaded nut, while axial detent surfaces on an offset housing boring abut the shoulders of the outer rings. A disadvantage of this design is the excessively large, axially, occupied space of the drive, since both bearings of the bearing pairs must be installed in the space on the output side beside the planetary set, while in the neighborhood of the input drive shaft, unused space is still available. Because of the restricted axial separating distance of the two bearings, the bearing distance for effective bearing kinematics is small, in spite of the O-arrangement.
Thus, the invention has the purpose to make available a planetary drive, in which the bearing of an axially installed, inclined bearing pair, is arranged in such a manner, that a simple mounting operation, a small construction expense, and an easily inspected construction are achieved, comparable to a gear drive, in which the bearings are placed in an X-arrangement, and whereby at the same time, a higher load capacity and structural strength and as precise a running condition is achieved as is the case with the X-arrangement.
Utilizing as a starting point, a planetary drive with the features of the principal concept of the main claim, wherein the planet carrier, in common with a output side output shaft, is seated in bearings formed by an axially placed first and a second inclined bearing pair, the purpose of the invention is achieved, in that at least the first inclined bearing pair is fixed in the housing with its inner ring, and its outer ring rotates with the planet carrier and the pressure lines of the said pair forms a pressure cone, the apex of which is pointed away from the second inclined bearing.
Where the invented planetary drive is concerned, the planet carrier can be installed in the same advantageous manner as in the case of a drive with the X-arrangement, wherein, in any case, the bearing distance for effective bearing kinematics is essentially greater.
In an advantageous embodiment of the invention, the first inclined bearing is on one side of an axial, planetary plane running through the planetary gears. The second inclined bearing is placed on the other side of the planetary gear plane. This embodiment offers a very large axial bearing distance for effective bearing kinematics within a short length of construction space.
Should very large torque moments be taken up by the output shaft, then both bearing can be so disposed, that the inner rings are affixed in the housing and the outer rings turn with the planet carrier, whereby the apexes of both pressure cones point away from each other. Thereby, the same kinematically effective bearing characteristics are achieved as are found in the O-arrangement.
However, it is often sufficient if only the first inclined bearing has its inner ring affixed in the housing and the inner ring of the second inclined bearing has its inner ring rotating in the planet carrier and its outer ring is affixed in the housing. In this case, the second inclined bearing with its pressure lines forms a pressure cone, the apex of which points toward the first inclined bearing. In this way, a parallel arrangement of the pressure cones is created, so thatxe2x80x94with the use of the same bearingsxe2x80x94the axial bearing distance for effective bearing kinematics is equal to the actual axial distance of the bearing.
In an embodiment of this formulation, the apexes of the pressure cones of the two inclined bearings point away from the output side of the drive, whereby a simple construction mode is achieved. In the case of an alternative embodiment the apexes of the pressure cones of the two inclined bearings point toward the output side of the drive, so that the bearing base is pushed in an advantageous manner toward the output shaft.
Since the planet carrier rotates within the housing, it is necessary to provide means, which enable the outer ring to be assigned to the planet carrier and the inner ring to the housing. In an advantageous manner, this can be done, in that the planet carrier, for the reception of the outer ring of the inclined bearing, possesses a tubular shaped extension and/or that the housing, for the reception of the inner ring, has a cylindrical projection. This said projection would be enclosed in an annular recess in the housing, which can accept this inclined bearing and at least partially, the tubular shaped extension of the planet carrier.